Opponents of California’s Proposition 8, which on Tuesday successfully restored the definition of marriage to be between one man and one woman, have filed suit asking the California Supreme Court to overturn the measure. Counsel for the Yes on 8 campaign responded, calling the lawsuits “frivolous and regrettable.”

The lawsuits were filed by lawyers for same-sex couples that received state marriage licenses during the recent period in which the Supreme Court mandated that homosexual marriages be recognized.

The plaintiffs argue that Proposition 8 rises to the level of a constitutional revision because it fundamentally altered the guarantee of equal protection. Further, they claim that Prop. 8 is illegal because a constitutional revision must be approved by the legislature before being proposed to voters.

Joseph Grodin, a former California Supreme Court justice and an opponent of Proposition 8 who assisted in earlier legal challenges to the measure, said he believes the argument has legal merit.

The state’s high court has struck down ballot measures as illegal constitutional revisions twice before, but Grodin said the proposals involved “a broader scope of changes.”

The lawsuit, which was filed by the American Civil Liberties Union (ACLU) and Equality California was soon joined by another from the lesbian couple that was the first to be married after the Supreme Court overruled California voters previous ban on gay marriage. The San Francisco City Attorney’s office has also told the San Diego Union Tribune that “he plans to challenge the validity of a ballot measure that would change the state constitution to ban gay marriage.”

“If they want to legalize gay marriage, what they should do is bring an initiative themselves and ask the people to approve it," Schubert said to the Los Angeles Times. “But they don't. They go behind the people's back to the courts and try and force an agenda on the rest of society."

The General Counsel of ProtectMarriage.com – Yes on 8, Andrew Pugno, called the lawsuit by the ACLU “frivolous and regrettable,” characterizing it as an attempt to “invalidate the decision of California voters to enshrine traditional marriage in California's constitution.”

“These same groups filed an identical case with the California Supreme Court months ago, which was summarily dismissed,” Pugno said in a Wednesday statement. “We will vigorously defend the People's decision to enact Proposition 8.”

According to Pugno, the ACLU made the same “constitutional revision” claim in a “nearly identical matter” in Oregon concerning that state’s marriage amendment. Their claim, decided in the Oregon case Martinez v. Kulongoski, was unanimously rejected.

"This is the second time that California voters have acted to define marriage as between a man and a woman,” Pugno continued. “It is time that the opponents of traditional marriage respect the voters' decision.”

He also attacked the lawsuit as “completely lacking in merit.”

“It is as if their campaign just spent $40 million on a losing campaign opposing something they now say is a legal nullity. Their position is absurd, an insult to California voters and an attack on the initiative process itself.”

Pugno argued that the right to amend California’s constitution is not “granted to the People,” but rather “reserved by the People.” He cited as precedent a California Supreme Court ruling which held that the death penalty was a “violation of fundamental state constitutional rights,” a decision overturned through the state’s initiative amendment process.

“Even a liberal jurist who vehemently disagreed with the People's decision on the death penalty, Justice Stanley Mosk, nevertheless acknowledged the People's authority to decide the issue through the initiative-amendment process,” he noted.

"The coalition that has worked so hard for the past year to enact Proposition 8 will vigorously defend the People's decision against this unfortunate challenge by groups who, having lost in the court of public opinion, now turn to courts of law to pursue their agenda," Pugno concluded.